1. Field of the Invention
The present invention relates to valves in general, and more particularly to a fluid material flow control valve adapted to be remotely actuated by pneumatic or fluid means. The present invention is particularly adapted for use in connection with abrasive blasting systems where it is necessary to control the flow of abrasive media from one part of the system to another, for example, from a hopper to the system's abrasive media holding tank, or to control and modulate the flow of abrasive from the abrasive media holding tank to the abrasive blast hose. However, the other possible uses of the valve are manifold. In its various embodiments as described below the present invention is capable of handling and controlling the flow of almost any material capable of being moved through a conduit including gases, liquids, and particulate materials ranging in size from large diameter aggregate down to extremely fine powders.
2. Description of the Prior Art
Valves which control fluid material flow are well known. For example, it is known to control the gravity flow of abrasive media, such as sand, through a pipe by means of a pinch valve which can either be mechanically or pneumatically actuated. Such a pinch valve operates by simply pinching closed a flexible section of tubing through which the abrasive media flows. The pneumatic version of the pinch valve, which has the advantage of being remotely controllable, essentially consists of a length of flexible tubing surrounded by an air tight housing with means for pressuring the housing to pneumatically pinch closed the section of the tubing disposing therein.
The great disadvantage with the pneumatic pinch valve, as well as other commercially available valves, is that it is a normally open valve. Should for any reason there be a loss of pressure to the valve, such as, for example, due to a leak in an air supply line, then the valve would automatically open allowing an undesired flow of fluid material therethrough. The consequences of such an undesired flow can in many circumstances be costly. It can also create a hazardous condition such as an uncontrolled blast of abrasive, or an environmentally undesirable condition such as the accidental loss of crude oil from a pipe line or loading line hose.
The present invention overcomes the disadvantage of the conventional pneumatic pinch valve by providing a fluid material flow control valve which, though also pneumatically actuated, is normally closed and fail safe. In the present invention loss of pneumatic integrity will cause the valve to close, or remain closed, thereby preventing fluid material from flowing through the valve until suitable repairs can be made. The present invention also combines the advantage of a variable control capability wherein the invention can be adapted not only to an "on-off" function but also to a flow rate control function. The present invention has the further advantage of being adaptable to many different uses involving the control of fluid material flow, this because of the valve's unique capability of handling fluid materials of all forms (gas, liquid, particulate) and in extreme environments.